Spindle motor

ABSTRACT

There is provided a spindle motor including: a shaft; a first sleeve rotatably supporting the shaft by fluid dynamic pressure; a second sleeve provided outwardly of the first sleeve; a stator core mounted on an outer surface of the second sleeve; and a base member including a mounting part protruding upwardly in an axial direction and fixed to at least one of the first and second sleeves.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Applications No.10-2012-0032342 filed on Mar. 29, 2012 and No. 10-2012-0062637 filed onJun. 12, 2012, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein by references.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spindle motor.

2. Description of the Related Art

A hard disk drive (HDD), an information storage device, reads datastored on a disk or writes data to a disk using a read/write head.

The hard disk drive requires a disk driving device capable of driving adisk. In the disk driving device, a small spindle motor is used.

This small-sized spindle motor has used a hydrodynamic bearing assembly.A shaft, a rotating member of the hydrodynamic bearing assembly, and asleeve, a fixed member thereof, have a lubricating fluid interposedtherebetween, such that the shaft is supported by pressure generated inthe lubricating fluid.

In addition, a rotor hub rotating together with the shaft and having arecording disk mounted thereon may be disposed on an upper portion ofthe shaft, and the rotor hub is fixedly coupled to the upper portion ofthe shaft and has a disk shape in which it is extended in a radialdirection based on the shaft. Therefore, the lubricating fluid may alsobe interposed between an upper surface of the sleeve and the rotor hub.

According to the related art, in manufacturing a base provided in thehard disk drive, a post-processing scheme of die-casting aluminum (Al)and then removing burrs or the like, generated due to the die-castingprocess has been used.

However, in the die-casting scheme according to the related art, since aprocess of injecting aluminum (Al) in a molten state into a mold to makea form is performed, large amounts of temperature and pressure arerequired, such that a large amount of energy may be required in theprocess and processing time and costs may be increased.

Therefore, in order to solve the problems of the die-casting process, anattempt to manufacture the base through a plastic working process suchas press working, or the like, has been conducted. However, in the caseof manufacturing the base by press working, since the base may have auniform thickness, a problem may be generated in coupling a core to thebase.

That is, in the case in which a base is manufactured in a die-castingprocess, the base may be provided with a step, so as to seat the corethereon. However, in the case in which a base is manufactured bypressing a plate material having a uniform thickness, since thethickness of the base is uniform, it may be difficult to form a coreseating part on the base.

Japanese Patent Laid-Open Publication No. 2007-198555 discloses that adie-casting base is provided with a step to seat a core thereon.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a spindle motor in which acore may be stably and easily seated on a base manufactured by plasticworking such as press working, or the like.

According to an aspect of the present invention, there is provided aspindle motor including: a shaft; a first sleeve rotatably supportingthe shaft by fluid dynamic pressure; a second sleeve provided outwardlyof the first sleeve; a stator core mounted on an outer surface of thesecond sleeve; and a base member including a mounting part protrudingupwardly in an axial direction and fixed to at least one of the firstand second sleeves.

The second sleeve may be provided with a core seating part protrudingoutwardly and having the stator core seated thereon.

An upper surface or a lower surface of the stator core may be bonded tothe core seating portion.

The shaft may include a hub coupled to an upper end thereof, a thrustdynamic pressure bearing may be formed between the hub and a surface ofthe first sleeve facing the hub, a radial dynamic pressure bearing maybe formed between the shaft and a surface of the first sleeve facing theshaft, and parallelism between a surface of the core seating part onwhich the core is seated and the surface of the first sleeve in whichthe thrust dynamic pressure bearing is formed may be 50 μm or less.

The shaft may include a hub coupled to an upper end thereof, a thrustdynamic pressure bearing may be formed between the hub and a surface ofthe first sleeve facing the hub, a radial dynamic pressure bearing maybe formed between the shaft and a surface of the first sleeve facing theshaft, perpendicularity between a surface of the core seating portion onwhich the core is seated and the surface of the first sleeve in whichthe radial dynamic pressure bearing is formed may be 50 μm or less.

The shaft may include a hub coupled to an upper end thereof, the hubincluding a main wall portion extended downwardly in the axial directionso as to have an inner surface facing at least a portion of an outersurface of the first sleeve and an outer surface facing at least aportion of an inner surface of the second sleeve.

The outer surface of the main wall portion and the inner surface of thesecond sleeve may form a labyrinth seal.

The mounting portion may be fitted between the first and second sleeves.

The mounting portion may be coupled to the second sleeve, and an outersurface of a lower end of the first sleeve may be inclined inwardly froman upper portion thereof toward a lower portion thereof.

The first and second sleeves may include at least one oil injection holepenetrating therebetween in the axial direction.

The first and second sleeves may be formed integrally with each other.

The base member may be formed by performing plastic working on a rollingsteel sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1 through 3 are schematic cross-sectional views showing a spindlemotor according to embodiments of the present invention; and

FIG. 4 is a schematic cross-sectional view of a disk driving deviceusing a spindle motor according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings. However, it should be notedthat the spirit of the present invention is not limited to theembodiments set forth herein and that those skilled in the art andunderstanding the present invention could easily accomplishretrogressive inventions or other embodiments included in the spirit ofthe present invention by the addition, modification, and removal ofcomponents within the same spirit, but those are to be construed asbeing included in the spirit of the present invention.

Further, when it is determined that the detailed description of theknown art related to the present invention may obscure the gist of thepresent invention, the detailed description thereof will be omitted.

FIG. 1 is a schematic cross-sectional view showing a spindle motoraccording to an embodiment of the present invention.

Referring to FIG. 1, a spindle motor 100 according to the embodiment ofthe present invention may include a hydrodynamic bearing assembly 110including a shaft 111, a first sleeve 112-1, a rotor hub 121, a stopper111 a, and a cover member 113, a rotor 120 including the rotor hub 121,and a stator 130 including a core 131 having a coil 132 woundtherearound.

The hydrodynamic bearing assembly 110 may include the rotor hub 121.Here, the rotor hub 121 may be a component configuring the hydrodynamicbearing assembly 110 while configuring the rotor 120 to be describedbelow.

In addition, a rotating member assembly may include the shaft 111 andthe rotor hub 121 mounted on the shaft 111.

In addition, a sleeve 112 may include the first sleeve 112-1 and asecond sleeve 112-3 to be described below.

Terms with respect to directions will first be defined. As viewed inFIG. 1, an axial direction refers to a vertical direction based on theshaft 111, and an outer radial direction and an inner radial directionrefers to a direction toward an outer edge of the rotor hub 121 based onthe shaft 111 and a direction toward the center of the shaft 111 basedon the outer edge of the rotor hub 121, respectively.

Further, in the following description, a rotating member may include arotating member such as the shaft 111, the rotor 120 including the rotorhub 121, a magnet 125 mounted on the rotor 120, and the like, while afixed member may include members other than the rotating member andrelatively fixed to the rotating member, such as the first sleeve 112-1,the second sleeve 112-3, the stator 130, a base member 133, and thelike.

In addition, a communication path between an interface of a lubricatingfluid and the outside means a path through which the interface of thelubricating fluid is connected to the outside of the spindle motor andmay have air introduced and discharged therethrough.

The first sleeve 112-1 may support the shaft 111 so that an upper end ofthe shaft 111 protrudes upwardly in an axial direction. The first sleeve112-1 may be formed by forging Cu or Al or sintering a Cu—Fe-based alloypowder or a SUS-based powder. However, the sleeve is not limited tobeing manufactured by the above-mentioned method, but may bemanufactured by various methods.

Here, the shaft 111 may be inserted into a shaft hole of the firstsleeve 112-1 so as to have a micro clearance therebetween, therebyforming a bearing clearance C. The bearing clearance C may be filledwith the lubricating fluid (or oil) (hereinafter, both “lubricatingfluid” and “oil” are used interchangeably). At least one of an outerdiameter of the shaft 111 and an inner diameter of the first sleeve112-1 may be provided with upper and lower radial dynamic pressuregrooves 114. At the time of rotation of the rotor 120, a radial bearingmay be generated by the radial dynamic pressure groove 114, and therotor may rotate smoothly due to the radial bearing.

The spindle motor 100 according to the embodiment of the presentinvention may use a fluid bearing and generally include a pair of upperand lower radial dynamic pressure grooves for rotational stability, suchthat two hydrodynamic bearings may be formed when the motor is driven.

That is, the radial dynamic pressure grooves 114 may generate fluiddynamic pressure at the time of the rotation of the shaft 111 so thatthe shaft 111 may rotate smoothly in a state in which the shaft isspaced apart from the first sleeve 112-1 by a predetermined interval,thereby serving as a bearing.

However, the radial dynamic pressure grooves 114 are not limited tobeing formed in the inner side of the first sleeve 112-1 as describedabove, but may also be formed in an outer diameter portion of the shaft111. In addition, the number of radial dynamic pressure grooves 114 isnot limited.

Here, the radial dynamic pressure groove 114 may have any one of aherringbone shape, a spiral shape, and a helical shape. However, theradial dynamic pressure groove 114 may have any shape as long as radialdynamic pressure may be generated thereby.

The first sleeve 112-1 may be provided with a circulation hole 117allowing upper and lower portions thereof to be in communication witheach other. The circulation holes 117 may disperse pressure of thelubricating fluid in the hydrodynamic bearing assembly 110 to maintainbalance in the pressure of the lubricating fluid and allow air bubbles,or the like, present in the inner portion of the hydrodynamic bearingassembly 110 to move so as to be discharged by circulation.

Here, the shaft 111 may include the stopper 111 a provided on a lowerend portion thereof and protruding in the outer radial direction, andthe stopper 111 a may be caught by a lower end surface of the firstsleeve 112-1 to limit floatation of the shaft 111 and the rotor 120.

Meanwhile, a groove shaped reservoir part 115 may be formed in at leastone of the first sleeve 112-1 and the shaft 111 between the upper andlower radial dynamic pressure grooves 114 so that the bearing clearancebetween the first sleeve 112-1 and the shaft 112 may be wider therein,as compared to other portions. Although the case in which the reservoirpart 115 is provided on an inner peripheral surface of the first sleeve112-1 in a circumferential direction is shown in FIG. 1, the presentinvention is not limited thereto. The reservoir part 115 may be providedon an outer peripheral surface of the shaft 111 in the circumferentialdirection.

In addition, the first sleeve 112-1 may include a thrust dynamicpressure groove formed in an upper surface thereof to generate thrustdynamic pressure at the time of the rotation of the shaft. The thrustdynamic pressure groove is not limited to being formed in the firstsleeve 112-1, but may also be formed in the rotor hub 121 facing theupper surface of the first sleeve 112-1. The thrust dynamic pressuregroove may have various shapes, such as a spiral shape, a herringboneshape, a helical shape, and the like.

Meanwhile, the cover member 113 may be coupled to the lower portion ofthe first sleeve 112-1 in the axial direction while covering the shafthole of the first sleeve 112-1 to prevent leakage of the lubricatingfluid.

Here, the cover member 113 may receive the lubricating fluid in aclearance formed between a lower surface of the shaft 111 and the covermember 113, thereby serving as a bearing supporting the lower surface ofthe shaft 111 at the time of the rotation of the shaft 111.

The second sleeve 112-3 may be provided on an outer surface of the firstsleeve 112-1. The first sleeve 112-1 positioned at the inner side of thesecond sleeve 112-3 may serve to support the shaft 111 and form thehydrodynamic bearing assembly, and the second sleeve 112-3 positioned atthe outer side of the first sleeve 112-1 may serve to fix a stator core131 to be described below.

A main wall part 126 extended from a rotor hub 121, to be describedbelow, downwardly in the axial direction may have an inner surfacefacing at least a portion of the outer surface of the first sleeve 112-1and an outer surface facing at least a portion of an inner surface ofthe second sleeve 112-3. That is, the main wall part 126 may be disposedbetween the first and second sleeves 112-1 and 112-3. In this case, theouter surface of the main wall part 126 and the inner surface of thesleeve 112-3 may form a labyrinth seal. Therefore, scattering or leakageof the oil may be significantly reduced.

More specifically, the first and second sleeves 112-1 and 112-3 may beconnected to each other through a connecting part 112-2. The connectingpart 112-2 indicates a portion at which the first and second sleeves112-1 and 112-3 are connected to each other.

Here, the connecting part 112-2 may have an axial length shorter thanthose of the first and second sleeves 112-1 and 112-3 and connect thefirst and second sleeves 112-1 and 112-3 to each other at anapproximately central portion thereof in the axial direction. Therefore,upper and lower spaces between the first and second sleeves 112-1 and112-3 may be formed based on the connecting part 113.

Meanwhile, the first and second sleeves 112-1 and 112-3 may be formedseparately from or integrally with each other. That is, the first sleeve112-1 and the connecting part 112-2, the connecting part 112-2 and thesecond sleeve 112-3, or the first sleeve 112-1, the connecting part112-2, and the second sleeve 112-3 are formed integrally with eachother, whereby the number of components may be reduced. When the numberof components is reduced, a product may be manufactured by a singlecutting process without coupling between components, so that a couplingtolerance according to coupling between components may not be generated,and thus, a coupling degree of the product may be increased. The firstsleeve 112-1, the connecting part 112-2, and the second sleeve 112-3 maybe formed of the same material.

In addition, the first and second sleeves 112-1 and 112-2 may include atleast one oil injecting hole 112 a penetrating therebetween in the axialdirection. More specifically, the connecting part 112-2 which is aconnection portion of the first and second sleeves 112-1 and 112-2 mayinclude at least one oil injecting hole 112 a penetrating therethroughin the axial direction.

Here, the axial direction may include the same direction as the axialdirection or a slightly inclined direction. The oil injecting hole 112 ais provided to complete the hydrodynamic bearing assembly 100 and allowoil to be easily injected into the bearing clearance C. The oil may alsobe injected into the bearing clearance C by other methods, without usingthe oil injecting hole 112 a.

Further, an upper end of the second sleeve 112-3 is provided with a coreseating part 112-4 protruding outwardly to allow an upper portion of thecore 131 to be caught, such that a fixed position of the core may beguided. The core 131 may be bonded to the core seating part 112-4.

In this case, parallelism between a surface of the core seating part112-4 on which the core 131 is seated and the upper surface of the firstsleeve 112-1 in which the thrust dynamic pressure bearing is formed maybe 50 μm or less, and perpendicularity between the surface of the coreseating part 112-4 on which the core 131 is seated and the inner surfaceof the first sleeve 112-1 in which the radial dynamic pressure bearingis formed may be 50 μm or less. That is, error ranges of the parallelismand the perpendicularity may be 50 μm or less. In the case in which thefirst and second sleeves 112-1 and 112-3 are formed integrally with eachother, it may be easy to process the first and second sleeves 112-1 and112-3 simultaneously to reduce the error range.

In addition, a mounting part 134 protruding from the base member 133upwardly in the axial direction may be fixed to at least one of thefirst and second sleeves 112-1 and 112-3. In more detail, the mountingpart 134 may be fitted into and coupled to the space formed between thefirst and second sleeves 112-1 and 112-3. That is, the mounting part 134may be fitted into the space formed between the first and second sleeves112-1 and 112-3.

In the case in which the mounting part 134 is fitted into and coupled tothe space formed between the first and second sleeves 112-1 and 112-3,the mounting part 134 may be bonded to at least one of the first andsecond sleeves 112-1 and 112-3. That is, a bond is applied to the spaceformed between the first and second sleeves 112-1 and 112-3, and themounting part 134 may be slid and coupled to the space to thereby befixed thereto. In the case, the bond may be applied to at least any oneof the first and second sleeves 112-1 and 112-3.

Further, the coupling method is not limited to the sliding or bondingmethod but may also use a press-fitting method, a welding method, or thelike. In the case of the press-fitting method, the mounting part 134 maybe press-fitted into at least one of the first and second sleeves 112-1and 112-3.

The rotor hub 121, a rotating member coupled to the shaft 111 androtating together with the shaft 111, may configure the rotor 120 whileconfiguring the hydrodynamic bearing assembly 110. Hereinafter, therotor 120 will be described in detail.

The rotor 120 may be a rotating structure provided to be rotatable withrespect to the stator 130 and include the rotor hub 121 having themagnet 125 provided on an inner peripheral surface thereof and having anannular ring-shape, wherein the annular ring-shaped magnet 125corresponds to the core 131 to be described below, having apredetermined interval therebetween.

In other words, the rotor hub 121 may be a rotating member coupled tothe shaft 111 to rotate together with the shaft 111. Here, the shaft 111and the rotor hub 121 may include an adhesive applied therebetween tothereby be fixed to each other. However, the shaft 111 and the rotor hub121 are not limited to being fixed to each other in the above-mentionedmethod, but may be fixed to each other in various fixing methods such asa welding method, a press-fitting method, and the like.

Here, the magnet 125 may be a permanent magnet generating magnetic forcehaving predetermined strength by alternately magnetizing an N pole andan S pole thereof in a circumferential direction.

In addition, the rotor hub 121 may include a first cylindrical wall part122 fixed to an upper end portion of the shaft 111, a disk part 123extended from an end portion of the first cylindrical wall part 122 inthe outer radial direction, and a second cylindrical wall part 124protruding downwardly from an end portion of the disk part 123 in theouter radial direction. The second cylindrical wall part 124 may includethe magnet 125 coupled to an inner peripheral surface thereof.

The rotor hub 121 may include the main wall part 126 extended downwardlyin the axial direction so as to correspond to an outer portion of theupper portion of the sleeve 112. In more detail, the rotor hub 121 mayinclude the main wall part 126 extended from the disk part 123downwardly in the axial direction and disposed between the first andsecond sleeves 112-1 and 112-3.

A liquid-vapor interface sealing the lubricating fluid maybe formedbetween the outer surface of the first sleeve 112-1 and the innersurface of the main wall part 126. In addition, the labyrinth seal maybe formed between the inner surface of the second sleeve 112-3 and theouter surface of the main wall part.

Further, the inner surface of the main wall part 126 may be tapered,such that an interval between the inner surface of the main wall part126 and the outer surface of the first sleeve 112-1 may grow widerdownwardly in the axial direction, so as to facilitate the sealing ofthe lubricating fluid. Further, the outer surface of the first sleeve112-1 may also be tapered to facilitate the sealing of the lubricatingfluid.

The stator 130 may include the coil 132, the stator core 131, and thebase member 133.

In other words, the stator 130 may be a fixed structure including thecoil 132 generating electromagnetic force having a predeterminedmagnitude when power is applied thereto, and a plurality of stator cores131 having the coil 132 wound therearound.

The core 131 may be fixedly disposed above the base member 133 includinga printed circuit board (not shown) having circuit patterns printedthereon, a plurality of coil holes having a predetermined size may beformed in the base member 133 corresponding to the wound coil 132 so asto penetrate through the base member 133 in order to expose the woundcoil 132 downwardly, and the wound coil 132 may be electricallyconnected to the printed circuit board (not shown) so that externalpower may be supplied thereto.

Here, the base member 133 may include the mounting part 134 protrudingupwardly in the axial direction.

The base member 133 may be manufactured by performing plastic working ona rolled steel sheet. More specifically, the base member 133 may bemanufactured by a pressing method, a stamping method, a deep drawingmethod, or the like. However, the base member 133 is not limited tobeing manufactured by the above-mentioned methods, and may bemanufactured by various methods that are not described herein.

The base member 133 may be assembled by fitting the mounting part 134into the space formed between the first and second sleeves 112-1 and112-3 and applying an adhesive to the space formed between the first andsecond sleeves 112-1 and 112-3.

Here, as a method of fixing the mounting part 134 thereto, a slidingmethod, a press-fitting method, or a welding method, as well as abonding method, may be used.

Meanwhile, the core 131 having the coil 132 wound therearound may befixedly coupled to the outer surface of the second sleeve 112-3. In thiscase, the upper end of the second sleeve 112-3 is provided with the coreseating part 112-4 protruding outwardly therefrom to allow the core 131to be caught at the upper portion thereof, such that the fixed positionof the core may be guided.

Further, the core 131 may be fitted into and coupled to the outersurface of the second sleeve 112-3 after the bond is applied to theouter surface of the second sleeve 112-3. However, the core 131 is notlimited to being fixed by the above-mentioned fixing method, but may befixed by various fixing methods such as a sliding method, apress-fitting method, a welding method, and the like.

FIG. 2 is a schematic cross-sectional view showing a spindle motoraccording to another embodiment of the present invention.

Referring to FIG. 2, a spindle motor 200 according to another embodimentof the present invention may be different from the spindle motor 100according to the embodiment of the present invention described withreference to FIG. 1, in terms of a shape of the connecting partconnecting first and second sleeves 112-1 and 112-3 to each other.Therefore, the spindle motor 200 may be different in terms of a couplingshape between the first sleeve 112-1 and a base member 133 from thespindle motor 100. Therefore, a detailed description of the samestructure and shape will be omitted in order to prevent confusion andmake a description of the present invention clear. Hereinafter, featuresdifferent from those of the spindle motor 100 described with referenceto FIG. 1 will mainly be described.

A connecting part 112-5 used in the spindle motor 200 according to theembodiment of the present invention may connect the first and secondsleeves 112-1 and 112-5 to each other. In addition, the connecting part112-5 may have an axial length slightly shorter than those of the firstand second sleeves 112-1 and 112-3.

However, the connecting part 112-5 may connect the first and secondsleeves 112-1 and 112-5 to each other at a lower portion of the secondsleeve 112-3 in the axial direction. Therefore, a space between thefirst and second sleeves 112-1 and 112-3 may be formed above theconnecting part 112-5, but may not be formed thereunder.

Therefore, the mounting part 143 of the base member 133 may be mountedto face the lower surface of the second sleeve 112-3. An additionalcoupling method such as an adhesive bonding method, a sliding method, awelding method, or the like, may be similarly utilized. Since themounting part 134 is coupled to the second sleeve 112-3, an outersurface of a lower end of the first sleeve 112-1 may be inclinedinwardly from an upper portion thereof toward a lower portion thereof.Due to this shape, an adhesive may be easily applied thereto or weldingmay be easily performed.

FIG. 3 is a schematic cross-sectional view showing a spindle motoraccording to another embodiment of the present invention.

Referring to FIG. 3, a spindle motor 300 according to the embodiment ofthe present invention may be different from the spindle motor 100described above with reference to FIG. 1, in terms of a position of acore seating part 112-6 provided in the second sleeve 112-3. Therefore,a detailed description of the same structure and shape will be omittedin order to prevent confusion and make a description of the presentinvention clear. Hereinafter, features different from those of thespindle motor 100 described above with reference to FIG. 1 will bemainly described.

The core seating part 112-6 used in the spindle motor 300 according toanother embodiment of the present invention protrudes outwardly from thesecond sleeve 112-3 to allow the lower portion of the stator core 131 tobe caught, such that a fixed position of the stator core 131 may beguided thereby. That is, unlike the spindle motor 100 according to theembodiment of the present invention described with reference to FIG. 1,the core seating part 112-6 may be positioned lower than the stator core131 in the axial direction. The core 131 may be bonded to the coreseating part 112-6.

Although a shaft-rotating type structure in which the rotor hub iscoupled to the shaft to rotate has been described in the embodiments ofFIGS. 1 through 7, the present invention may also have a shaft-fixingtype structure in which the rotor hub is coupled to the sleeve torotate.

FIG. 4 is a schematic cross-sectional view of a disk driving deviceusing a spindle motor according to an embodiment of the presentinvention.

Referring to FIG. 4, a recording disk driving device 800 having thespindle motor 100, 200, or 300 according to the embodiment of thepresent invention mounted therein is a hard disk driving device and mayinclude the spindle motor 100, 200, or 300, a head transfer part 810,and a housing 820.

The spindle motor 100, 200, or 300 may have all the characteristics ofthe spindle motor according to the embodiments of the present inventiondescribed above and may have a recording disk 830 mounted thereon.

The head transfer part 810 may transfer a magnetic head 815 detectinginformation of the recording disk 830 mounted on the spindle motor 100,200, or 300 to a surface of the recording disk from which information isto be read. Here, the magnetic head 815 may be disposed on a supportpart 817 of the head transfer part 810.

The housing 820 may include a motor mounting plate 822 and a top cover824 shielding an upper portion of the motor mounting plate 822 in orderto form an internal space receiving the spindle motor 100, 200, or 300and the head transfer part 810 therein.

As set forth above, in the spindle motor according to the embodiment ofthe present invention, the core may be stably and easily seated on thebase manufactured by the plastic working such as press working, or thelike.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.

1. A spindle motor comprising: a shaft; a first sleeve rotatablysupporting the shaft by fluid dynamic pressure; a second sleeve providedoutwardly of the first sleeve; a stator core mounted on an outer surfaceof the second sleeve; and a base member including a mounting partprotruding upwardly in an axial direction and fixed to at least one ofthe first and second sleeves, wherein a hub is coupled to the upper endof the shaft, a thrust dynamic pressure bearing is formed between thehub and a surface of the first sleeve facing the hub, and a radialdynamic pressure bearing is formed between the shaft and a surface ofthe first sleeve facing the shaft, the hub includes a main wall portionextended downwardly in the axial direction, the main wall portion isextended between the first sleeve and the second sleeve, and a lowersurface of the main wall portion is positioned below an upper surface ofthe first sleeve and the second sleeve, and the second sleeve isprovided with a core seating part protruding outwardly in the radialdirection and at least a part of an upper surface of the stator core isseated on the core seating part.
 2. (canceled)
 3. The spindle motor ofclaim 1, wherein the upper surface of the stator core is bonded to thecore seating part.
 4. The spindle motor of claim 1, wherein parallelismbetween a surface of the core seating part on which the core is seatedand the surface of the first sleeve on which the thrust dynamic pressurebearing is formed is 50 μm or less.
 5. The spindle motor of claim 1,wherein perpendicularity between a surface of the core seating part onwhich the core is seated and the surface of the first sleeve on whichthe radial dynamic pressure bearing is formed is 50 μm or less. 6.(canceled)
 7. The spindle motor of claim 1, wherein the outer surface ofthe main wall part and the inner surface of the second sleeve form alabyrinth seal.
 8. The spindle motor of claim 1, wherein the mountingpart is fitted between the first and second sleeves.
 9. The spindlemotor of claim 1, wherein the mounting part is coupled to the secondsleeve, and an outer surface of a lower end of the first sleeve isinclined inwardly from an upper portion thereof toward a lower portionthereof.
 10. The spindle motor of claim 1, wherein the first and secondsleeves includes at least one oil injection hole penetratingtherebetween in the axial direction.
 11. The spindle motor of claim 1,wherein the first and second sleeves are formed integrally with eachother.
 12. The spindle motor of claim 1, wherein the base member isformed by performing plastic working on a rolling steel sheet.